One of the fundamental principles underpinning the establishment of bowel cancer screening programmes for people with no symptoms is that early disease is detected. Treatment is then more effective, cure is often complete and survival is much enhanced. Significant evidence supports this thesis. It has been widely shown that more than half of all bowel cancers detected through screening programmes are early stage.
In Scotland, for example, the latest report issued in February 2016, containing data from May 2013 to April 2015,1 documents that 33% of cancers detected were Dukes’ A, the least advanced stage, 27% were Dukes’ B, 27% Dukes C1, and only 2% were Dukes’ C2 and 5% Dukes’ D, the most advanced stage.
But, an obvious question is: “how does this favourable stage distribution compare to bowel cancers detected in patients presenting with symptoms in primary care and also in patients presenting as emergencies to secondary care?” Two recent publications provide significant support that screening does indeed detect earlier stage cancers than other clinical presentations.
Comprehensive data released in January 2016 by Cancer Research UK (CRUK) and the National Cancer Intelligence Network (NCIN) allow comparison of the stages of bowel cancers arising from three paths of detection, namely, from screening, general practice as either an urgent referral requiring action within two weeks or as a routine referral, and presentation as emergency cases. 2 Of the cancers picked up by the NHS Bowel Cancer Screening Programme in England, more than 37% were detected at the earliest stage, while only 8% were at the most advanced stage. This compares to 40% of bowel cancers diagnosed as an emergency cases being at the most advanced stage and only 6% at the earliest stage. The data also showed that more than 22% of bowel cancers were at an advanced stage by the time people visited their GP and were subsequently found to have bowel cancer: only 18% of cancers in these symptomatic people were at the earliest stage.
A study from 2015 examined the impact of introduction of the Scottish Bowel Screening Programme in the West of Scotland. 3 In a population of 2.4 million, over a decade, 14 487 incident cases of bowel cancer were noted. After screening was begun, 18% were diagnosed via the screening programme. There was a reduction in emergency presentations (20% before screening against 13% after screening). An increase in the proportion of the earliest stage cancers at diagnosis was found (17% before screening against 28% after screening). It was concluded that a shift towards earlier stage at diagnosis had accompanied the introduction of the Screening Programme.
The results of these two recent studies demonstrate that bowel screening does “exactly what it says on the tin”. Participation in a screening programme does increase the chance that detection will be at an early, treatable stage if disease is present. In addition, if people with symptoms do follow the messages of the Detect Cancer Early Programme, the Be Clear on Cancer and similar campaigns, detection will again be at an earlier stage with all the resultant benefits. April is Bowel Cancer Awareness Month: it is hoped that these two timely messages receive further publicity then.
– Professor Callum G. Fraser
- Mansouri D, et al. Temporal trends in mode, site and stage of presentation with the introduction of colorectal cancer screening: a decade of experience from the West of Scotland. Br J Cancer 2015;113:556-61.